Coatings and paints represent an extremely large market for polymers. Particularly attractive from an application and safety perspective are so-called latex paints which are a water dispersion of polymer particles, usually prepared by emulsion polymerization. Although a significant reduction or elimination of volatile organic solvents is achieved by these products, the surfactants remaining after water evaporation, coupled with the relatively high molecular weight of the polymers, frequently prevent complete coalescence. Among other failure mechanisms, coatings may be composed of incompletely coalesced particles surrounded by surfactant. The latter represent buried hydrophiles running through the final coating which can readily absorb moisture. The result frequently is inadequate water resistance and, especially, poor wet adhesion, i.e., adhesion to a previously painted surface when wet.
A large number of polymerizable monomers have been proposed for enhancing wet adhesion of coatings and paints. Many of these materials are based on a polymerizable group attached to an imidazolidone (ethyleneurea), or another type of urea group. (Meth)acrylate and (meth)acrylamide units often have been employed to provide the polymerizable function for the monomer. Allylic functionality has also been used to provide a polymerizable function.
The following patents illustrate conventional wet adhesion monomers for use in preparing latex emulsions suited for paints:
British Patent 2 086 917 discloses wet adhesion promoters for aqueous film-forming surface coating compositions based upon acrylic functional ethylene ureas. In forming the wet adhesion monomer an ethylene urea or derivative is reacted with a hydroxy acrylate such as hydroxypropyl acrylate in the presence of a base.
U.S. Pat. No. 4,111,877 discloses wet adhesion monomers based on allyl esters of N-alkyl-omega-(alkylene ureido)carbamic acid in forming emulsion polymers suited for use in paints and coating compositions. The starting material for preparing the wet adhesion monomer is 2-aminoethylethyleneurea. It is formed by reacting diethylenetriamine with urea. The resulting ureido compound then is reacted with allyl chlorotormate to produce the allyl carbamate.
U.S. Pat. No. 3,369,008 discloses N-(cyclic ureido-alkyl) crotonamides for use as a wet adhesion monomers in coating and paint compositions. In the preparation of the wet adhesion monomer, a crotonic halide is reacted with an N-aminoalkyl-N,Nxe2x80x2-alkylene urea or thiourea.
U.S. Pat. No. 4,632,957 discloses wet adhesion monomers based on ethylenically unsaturated ethylene and propylene ureas and their use in preparing latex coating compositions. The wet adhesion monomers are prepared by reacting a primary amine or primary alcohol with a monoisocyanate having ethylenic unsaturation. Representative primary amines are based upon imidazolidones. Monoisocyanates having ethylenic unsaturation include isocyanato-ethyl methacrylate and isocyanato propyl methacrylate.
U.S. Pat. No. 5,496,907 discloses a new class of wet adhesion monomers containing a ureido group and optionally nitrile functionality. The ureido compound is formed by cyanoethylating an amino alkylethylene urea or an amino alkylene oxyalkylene ethyl urea. Ethylenic unsaturation is imparted by reducing the nitrile and reacting the resulting amine with a monoisocyanate having acrylic functionality such as isocyanatoethyl methacrylate.
U.S. Pat. No. 4,429,095 discloses cyclic alkylene ureas having residual unsaturation for use as wet adhesion promoters in latex paints. In forming the wet adhesion monomers a mono-(alkylene ureido alkyl) urea or a bis-(alkylene ureido alkyl) urea is reacted with an unsaturated glycidyl ether.
U.S. Pat. No. 5,739,196 discloses latex compositions incorporating wet adhesion promoting monomers. Examples include those primarily having acrylic functionality as the polymerizable unit for the wet adhesion promoting moiety. Specifically, N-(2-methacryloxylethyl)ethylene urea, dimethylaminopropyl acrylate, 2-N-morpholinoethyl acrylate are shown.